Tuning system for ultra-high-frequency radio apparatus



W. R KOCH May 9, 1939.

TUNING SYSTEM FOR ULTRA-HIGH-FHEQUENCY RADIO APPARATUS Filed June 30, 1936 2 Sheets-Sheet l v 1 3nventor attorney 1939, w. R. KOCH 2,157,855

TUNING SYSTEM FOR ULTRA-HIGH-FREQUENCY RADIO APPARATUS Filed June so, 1956 2 Sheets-Sheet 2 6/ I /6y 5. a

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, Gttorneg Fatented May 9, 1939 tion or fiware G srs'rarr ton or.

owner to Weld R. Koch, hierchantville, N. 3., t rim-i: Goration of America, a cor Application lie 3t, 1936, Serial No. @8365 The present invention relates to tuning system for ultra high frequency radio receiving apparatus and the like having operating frequencies in a range including 100 megacycles, and

- g has for its object to provide a tuning system for ultra high frequency apparatus of the character referred to wherein sliding and movable contacts in the high frequency circuits are eliminated.

It is also a further object of the present invention to provide an improved tuning control system for ultra high frequency radio apparatus and the like which is adapted for gang operation for simultaneously tuning a. plurality of circuits by single control means.- 15 It is also an object of the present invention to provide tunable high frequency coupling means for electric discharge or radio tube circuits wherein sliding contacts and movable circuit elements are eliminated.

The invention will be better understood from the following description, when considered in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Fig. l .is a schematiccircuit diagram of a tuning control system embodying the invention,

Fig. 21s a. similar schematic circuit diagram showing amodification of the circuit of Fig. 1 and also embodying the invention,

Fig. 3 is a schematic circuit diagram or an ultra high frequency oscillator provided with a tuning control system embodying the invention, and i Fig. 4 is a further modification of the invention showing an interstage tunable coupling system for ultra high frequency electric discharge tube circuits. I

Referring to Fig. 1', an electric discharge amplifier device 5 is provided with a signal or control grid 6 which is connected through a relatively short grid lead I with a signal input lead 8 for ultra high frequency radio signals and is also connected with a concentric or parallelwire line device 9 comprising a. central conductor iii and an outer sleeve or conductor ii forming an open ended ultra high frequency concentric tuned transmission line, the bottom or. low potential-end of which is closed, as indicated at i2, and connected to ground at it.

The input circuit and grid connection with the concentric line is made to the upper terminal end it of the central conductor and the line is preferably substantially a quarter wave length in length, for eple, about 29 inches for a frequency of megacycles.

All of the metallic connections and circuit leads are permanently made and secured by soldering or other suitable means, whereby loose or movable connections are prevented, and the input circuit for the tube 5 is tuned by moving a body of dielectric material it, such as rubber, or commercially mown dielectric materials like "Bakelite or Tsolantite, along the line between the conductors, from the closed to the open end thereof. Obviously for best selectivity, a good grade of dielectric material must be used.

The dielectric body is preferably solid and is provided with a central opening it through which the central conductor it iscarried and on which the dielectric body moves along the conductor, preferably substantially completely bridging the space between the outer conductor walls and the inner conductor, with a smooth sliding fit. The body of dielectric material i5. is moved downwardly, as viewed in the drawings,

to increase the frequency to which'the line is tuned. ,The highest frequency and shortest wave length is reached when the body it is moved iully to the closed (lower) end of the line. The length of the line thus determines the highest frequency to which the system may be tuned.

The dielectric body may be cylindrical in shape and of any suitable thickness to provide a desired change in the electrostatic field within the concentric line. This adds capacitive reactance across the line without changing the length of the line.

Any solid dielectric in a quarterwave length resonant line tends to lengthen the wave length to which it is resonant. The amount of lengthening is the least (resonant frequency highest) when the dielectric is near the closed end of the line and is largest (resonant frequency lowest) when it is at the open end, because it changes the dielectric along the line and thus lowers the velocity of the line when moved toward the open end.

sulating material, or by other suitable means, a change in the tuning of the line may be effected, and it has been found that the distance the dielectric must be moved to secure a given change in wave length is considerably more than in tuning means wherein a metallic contact is changed along a conductor. This gives a smoother tuning action or a vernier efiect, which permits easier adjustment of the tuning by manual means to By moving the dielectric as by a rod ll of inand tends to facilitate ganging or multiple unit control by a single operating means.

The tube 5 is provided with a self bias resistor I8 which is connected to ground I9 and to cathode 20 whereby the grid receives a bias potential therefrom. The tube may be of any suitable type, preferably of the pentode type for high gain or amplification.

The anode or output circuit of the tube may be tuned in a similar manner as the input circuit. and for this purpose is provided with a concentric line tuning device 2|, which may be similar to that provided for the input circuit, and is tunable in the same manner by means of a movable body of dielectric material 22 connected with a control rod 23.

In order that the tuning device 2| may be connected to ground at the closed end of the concentric line as indicated at 24, with positive potential on the anode, the output circuit is provided with a coupling resistor or impedance 25 and a coupling capacitor 26 interposed between the output anode indicated at 21 and the connection 28 with the central conductor 28. An output conductor 36 for ultra high frequency signals is also connected with the anode circuit 32 adjacent to the terminal 26.

With this arrangement, the tuning system described may provide coupling for interconnected or cascade connected amplifiers of the electric discharge tube type and the output lead 36 may be coupled in a similar manner as shown for the input lead 8, to a succeeding amplifier stage or other device (not shown) for which a tunable input circuit is required.

By interconnecting the control rods l1 and 23 by suitable means as indicated by the bar 3|, the latter may be moved to simultaneously actuate the tuning control dielectric bodies and may thereby provide unitary control of the tuning of a plurality of circuits as shown.

Referring now to Fig. 2, a modification of the coupling system of Fig. 1 is shown in which a pair of quarter wave length conductors 35 and 36 are arranged in parallel as shown and connected respectively to the anode 31 and the control grid 36 of two electric discharge devices 39 and 40 which are to be coupled in cascade for the amplification of ultra high frequency signals or oscillations. The opposite ends of the conductors 35 and 36 are curved toward each other to provide an end loop composed of the two conductors and completed through a capacitor. This may be provided by two plates 4| and 42 in close spaced relation to each other at the adjacent ends of the conductors.

With this arrangement the capacitor lies within the loop of the conductors 35 and 36, and forms part of the tunable circuit, the tuning of which is controlled by a movable body of dielectric material 43 through which the conductors extend and along which the dielectric material may be moved by suitable operating rods indicated at 44.

Anode potential is applied to the anode rod or conductor 35 at the closed or loop end thereof through a connection 45 adjacent to the capacitor. The connection includes a filter resistor 46 and bypass capacitor 41, for preventing coupling between the high frequency circuit and the potential supply means (not shown).

Likewise, the grid rod or conductor 36 is provided with a similar connection 48 adjacent to I the capacitor including a similar filter comprising a resistor 49 and bypass capacitor 50.

Tuning of the coupling system over a relatively wide high frequency range is accomplished by moving the dielectric material along the parallel twin conductor line formed by the rods 35 and 36 in conjunction with the capacitor 4I42.

Referring now to Fig. 3, an electric discharge oscillator device 55 of the pentode type is provided with a cathode 56 connected to chassis or ground 51 through a leak resistor 58 in shunt with a capacitor 59, and is provided with a control grid 60 connected through a short lead 6| with one of a pair of conductors 62-63 which terminate as a quarter wave length parallel line in the closed end 64 of an outer conductor 65 forming 9. cylindrical enclosure for the conductors 62 and 63.

The conductors are grounded as indicated at 66 and the second conductor 63 is connected at its upper end through a short lead 61 and a coupling capacitor 69 with the anode 68. A coupling impedance 10 in circuit with the anode is utilized to supply anode potential thereto. Oscillations are set up by coupling between the grid and plate circuits through the parallel conductor line which may be one quarter wave length in length, and the tuning of the line is accomplished by a movable plate of dielectric material H actuated by a control rod 12 to move along the line,,thereby providing a dielectric movable in the field between the inner. and outer conductors from the open to the closed end. Oscillations are derived from the oscillator circuit through output leads indicated at '|3I4.

Electro-magnetic coupling at ultra high frequencies may be obtained between two electric discharge amplifier devices with unitary control of tuning in the anode and grid circuits, by a system arranged in accordance with Fig. 1 but modified to include inductive coupling as shown in the circuit of Fig. 4 wherein the anode circuit of an electric discharge amplifier device 6! is tuned by a concentric line 82 containing a movable dielectric body 63, while circuit 84 to be coupled thereto is similarly tuned by a second concentric line 85, containing a movable dielectric body 86, both bodies being actuated by common control means indicated at 81.

The circuit 84 may be connected with a second stage amplifier tube 96 and is also connected at the open end 88 of the. inner conductor 89 of one concentric line while the anode circuit 80 is connected at the open end 90 of the inner conductor 9|.

Between the point of connection with the concentric tuned lines and each of the tubes, each of the circuits is formed in a loop and coupled thereby with the other circuit. The loop for the plate circuit is indicated at 92 and that for the grid circuit being indicated at 93. A single turn is suflicient for coupling when brought into coupling relation and an electro-static shield 84 connected to ground as indicated at 95 may be provided to prevent electro-static coupling. The concentric line in the anode circuit is connected to ground 91 through a bypass capacitor 98 while the concentric line for the grid circuit is connected directly to ground as indicated at 99.

From the foregoing description it will be seen that the output circuit of an amplifier stage may be coupled to the input circuit of a second amplifier stage through tunable concentric lines, with or without electro-magnetic coupling and without utilizing any tuning device incorporating fiexible'conductors or sliding or movable joints, whereby all tuned circuit elements maybe rigidly mounted and connected, and that the tuning of one or more concentric lines may be accomplished by moving a plate of cylindricalbody or dielectric material along ,the :line between the conductors thereof to tune the coupled circuits or toprovide coupling and tuning oitheelectrodes of an electric discharge device to provide ahigh frequency oscillator.

I claim as vmyinvention:

1. In an ultrahigh frequency signal transmission system, the combination with an ultra high frequency circuit, of means for tuning said circuit comprising a concentric tuned transmission line having a central conductor connected at its open end with the high potential side of said circuit, and means for variably controlling the tuning of said circuit and transmissionline, comprising a body of dielectric material movable axially along said line between the conductors thereof, whereby the circuit and concentric line may permanently be connected and variably tuned by the movable body of dielectric material as a capacitive reactance across the line without changing the eflfective length of line and without the intermediary of movable contacts and conductors.

2. In an ultra high frequency signal transmission system, the combination with a pair of ultra high frequency circuits, of means for tuning at least one of said circuits comprising a concentrictuned transmission line having a central conductor connected at its open end with the high potential side of said circuit, and being grounded at its opposite end, and means for variable controlling the tuning of said circuit and transmission line comprising a body of dielectric material movable axially along said line between the conductors thereof, whereby the ultra high frequency circuits and concentric line may permanently be connected and variably tuned by the movable body of dielectric material as a capacitive reactance across the line without changing the efiective length of the line and without the intermediary of movable contacts and conductors.

3. A signal transmission system in accordance with claim 1 further characterized by the fact that a second ultra high frequency circuit is provided therein and that a concentric tuned transmission line is provided for tuning said second circuit having a movable dielectric tuning control means connected with and simultaneously controllable by unitary common means with said first named tuning control means.

4. In a signal transmission system, the combination with a pair of ultra high frequency signal circuits, of a-concentric conductor tuned transmission line connected across each of said circuits, means for varying the tuning of each circuit in a range below the resonant frequency of the line, comprising a body of dielectric material of predetermined shape movable along and between the conductors of each of said lines to change the capacitive reactance along each line between the conductors from the closed to the open ends thereof, and unitary control means for moving said bodies of dielectric material axially along said lines to simultaneously vary the tuning in each of said circuits.

5. In a signal transmission system, the combination as defined in claim 4, further characterized by the fact that the tuned transmission lines are each one quarter wave length in length at the highest tunable frequency.

6. In a signal transmission system, the combination as defined in claim 4, further characterized by the fact'that said circuits are electromagnetically coupled only .by loops formed in the conductors thereof e rternal to said concentric lines.

'I. In a signaltransmission system, the combination asdeflnedin claim 4, further characteriz'edby the' fact that said circuits are coupled only by means external to said concentric lines.

8. In a signaltransmission system, the combination as'defined inclaim 4, further characterized by thefact that an electric discharge amplifier device having an input circuit and an output circuit is provided in connection with said ultra high frequency signal circuits.

9. In an ultra high frequency electric discharge'amplifier, the combination with a pair of electric discharge amplifier devices, of a parallel conductor quarter wave transmission line having adjacent ends thereof connected one-with each of said devices, means providing a capacitor for closing the opposite ends of said line, means including a series filter impedance for supplying operating potentials for said devices to said lines adjacent to said capacitor, and a body of dielectric material located between the conductors and movable along said line to vary the tuning thereof by varying the position of the dielectric ma- ,terial and its capacitive reactance across the line,

to alone provide a variable tuning means therefor by varying the position of the dielectric material and its capacitive reactance across the'line, without changing the length of the line or the circuit connections therewith, and means for moving said body of dielectric material to a predetermined position'of adjustment.

11. An ultra high frequency circuit comprising, in combination, an electric discharge device having'a cathode, a control grid and an output anode, a parallel conductor tuned transmission line having the conductors thereof connected at adjacent open ends, one with the grid and the other with the anode and having a closed opposite end connected with the cathode, means for varying the tuning of said transmission line in a range below the resonant frequency thereof, comprising a body of dielectric material movable along and between the conductors of said line to change the capacitive reactance at differing positions along said line from the closed toward the open ends of said conductors, whereby movable contacts in connection with said transmission line and variations in the length thereof are eliminated, and means for controlling the movement of said body of dielectric material along said line to varythe tuning thereof.

12. In an ultra high frequency signal system, the combination of a transmission line including a pair of conductors, and an insulation body movable along said line between said conductors to provide a movable capacitive reactance across the line for variably tuning ,said line.

13. In an ultra high frequency signal system, the combination of a transmission line including concentric conductors, and an insulation body providing a dielectric movable along said line between said conductors to provide a movable capacitive reactance across the line for variably tuning said line and for eliminating movable conductors and contacts in eflecting such variable tuning.

14. In an ultra high frequency signal system, the combination of a transmission line including parallel conductors connected together at one of their ends, and an insulation body movable longitudinally of and between said conductors to provide a movable capacitive reactance across the line for variably tuning said line and for eliminating movable conductors and contacts in effecting such variable tuning.

15. In a signal system, a transmission line including a pair of concentric conductors connected together at one of their ends, and an insulation body movable along and between said conductors to provide a movable capacitive reactance across the line for variably tuning said system, whereby movable contacts and conductors are eliminated. 10

WINFIELD R. KOCH. 

